HANOI, Vietnam — Vietnam's preference for boys over girls is further tipping the balance between the sexes in Asia, already skewed by a strong bias for boys among Chinese and Indians. The trend could lead to increased trafficking of women and social unrest, a U.N. report says.

Vietnam is now positioned where China was a decade ago, logging about 110 boys born to every 100 girls in a country where technology is readily available to determine the sex of a fetus and where abortion is legal, according to research released this week by the U.N. Population Fund.

The sex ratio at birth generally should equal about 105 boys to 100 girls, according to the report.

"The consequences are already happening in neighboring countries like China, South Korea and Taiwan. They have to import brides," said Tran Thi Van, assistant country representative of the Population Fund in Hanoi, adding that many brides are coming from Vietnam. "I don't know where Vietnam could import brides from if that situation happened here in the next 10 or 15 years."

'Marriage squeeze' predictedThe report, which looked at China, India, Vietnam and Nepal, warned that tinkering with nature's probabilities could cause increased violence against women, trafficking and social tensions. It predicted a "marriage squeeze," with the poorest men being forced to live as bachelors.

Gender imbalance among births has been rising in parts of Asia since the 1980s, after ultrasound and amniocentesis provided a way to determine a fetus' sex early in pregnancy. Despite laws in several countries banning doctors from revealing the baby's sex, many women still find out and choose to abort girls.

"I have noticed that there have been more and more boys than girls," said Truong Thi My Ha, a nurse at Hanoi's Maternity Hospital. "Most women are very happy when they have boys, while many are upset if they have girls."

In China, the 2005 estimate was more than 120 boys born to 100 girls, with India logging about 108 boys to 100 girls in 2001, when the last census was taken. However, pockets of India have rates of 120 boys. In several Chinese provinces, the ratio spikes to more than 130 boys born to 100 girls.

Reports of female infanticide still surface in some poor areas of countries and death rates are higher among girls in places like China, where they are sometimes breast-fed for shorter periods, given less health care and vaccinations and even smaller portions of food than their brothers, the report said.

It estimated Asia was short 163 million females in 2005 when compared to overall population balances of men and women elsewhere in the world. It said sex ratios at birth in other countries, such as Nepal, Pakistan and Bangladesh, also should be closely monitored to avoid uneven trends there.

Earlier research has documented the gender imbalance in the region. A UNICEF report last year estimated 7,000 girls go unborn every day in India.

Rates of women who are opting for preventive mastectomies, such as Angeline Jolie, have increased by an estimated 50 percent in recent years, experts say. But many doctors are puzzled because the operation doesn't carry a 100 percent guarantee, it's major surgery -- and women have other options, from a once-a-day pill to careful monitoring.

"It's very difficult to imagine what's going to be the exact impact of these missing girls in 20 years," said Christophe Guilmoto, an author of the report presented this week at a reproductive health conference in Hyderabad, India. "No human society that we know has faced a similar problem."

The reasons boys are favored over girls are complex and deeply rooted in Asian society. In many countries, men typically receive the inheritance, carry on the family name and take care of their parents in old age, while women often leave to live with their husband's family.

In India, wedding costs and dowries are usually required of the parents of the bride, and sons are the only ones permitted by the Hindu religion to perform the last rites when their fathers die.

"My husband took me to a private clinic to be checked. I broke down in tears when I saw the result because I knew this is not what my husband wanted," said Nguyen Thi Hai Yen, 33, recalling when she discovered her second baby was a girl. "But he was good. He told me it was OK."

China has a one-child policy, while Vietnam encourages only two children per family after relaxing an earlier ban on having more. Such limits have led many women to abort girls and keep trying for sons who can carry on the family lineage.

The report calls for increased public awareness, more government intervention and steps to elevate women's place in society by promoting gender equality.

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